Fuze systems, such as those used to initiate detonation of warheads in artillery shells, missiles, projectiles, or the like, must satisfy high performance criteria. These requirements have driven the direction of both mechanical and energetic materials designs. Energetic materials technology has moved to the use of explosive formulations that are less shock sensitive and have large critical diameters. The reduced shock sensitivity and large critical diameter focus serves to reduce the threat of hazard potential for impact shocks by bullet, fragments, and sympathetic detonation scenarios. This effect, while positive for meeting insensitive munitions requirements poses challenges for the fuze and initiation train designers who have to achieve reliable, prompt initiation of the explosive formulations during warhead function.
The maturing energetic material formulations have two different additional characteristics that further increase the difficulty of achieving proper initiation. The first is that many of the formulations are cast cured compounds that have a shrinkage rate upon curing. This potentially creates gaps between the fuze booster face and the bare explosive surface of the warhead. The second characteristic is based on design and terminal impact environments. The column height of the explosive fill, coupled with the dynamic impact decelerations causes the explosive to deform plastically, or flow, in the forward direction effectively increasing the booster gap in the aft-initiation design payloads. Prompt initiation of the insensitive munition explosive formulation requires a pressure front of sufficiently high magnitude and lengthy time period. The terminal conditions with various gaps require the high-impulse shock to be delivered across the gap.
Conventional booster designs have lightweight metal can designs that fail to deliver the pulse-length/high pressure shock front with uniformity into the explosive fill. The result is that the designs have low reliability and are much more likely to dud due to explosive shock quenching. Prior systems have attempted to compensate by placing a reduced size plug in the warhead representing the fuze during explosive loading in an attempt to minimize the gap between the fuze, booster and the explosive fill after curing. Since the shrinkage is a function of many parameters and can not be accurately predicted, this reduced but did not eliminate the gap. Additionally this process does not eliminate the explosive fill forward slosh during the terminal impact conditions.